Taking over for a legend is difficult enough but Quinn had to face some adversity early on. Left wing Matt Nieto left after his junior year to sign with the San Jose Sharks. Also, one of the team’s top defensemen, sophomore Matt Grzelcyk, a Bruins draft pick, was lost because of season-ending shoulder surgery. Those absences significantly affected the Terriers’ power play.

Other players jumped ship and others were let go.

Those adjustments left Quinn with a young squad — 17 players are either freshmen or sophomores — and the accompanying growing pains.

Now, the Terriers (10-20-4 overall, 5-12-3 in Hockey East) have their season on the line and need to beat Notre Dame in South Bend, Ind., Saturday night in a one-game elimination to stay alive and advance to the best-of-three Hockey East quarterfinals next weekend.

“There is a transition period for everybody when they climb the ladder in their profession,’’ said Quinn, 47. “You think you’re ready and then you do it and you say, ‘Wow, there’s more to it.’ There is a lot I’ve learned throughout this process. I always knew there was a lot more responsibility to the job besides coaching. You learn as you go.’’

Quinn said he knew some of the personnel decisions he made before the season were going to hurt short term but were made in the program’s best interest.

“Because of the decisions we made, we’re going to be better a lot quicker,’’ he said. “Maybe we would have won four or five more games, but that’s not what BU hockey wants to be. We want to compete for a national championship year in and year out. This year reminds me of 1988-89 when BU lost [21] games. The next year, they went to the Frozen Four. I’m not predicting we will go to the Frozen Four next year but we’ve got some great pieces here right now and with what we’ve got coming, I think we can make some drastic changes.’’

Parker made it clear right out of the gate that he wasn’t going to be looking over Quinn’s shoulder but he would offer himself as a resource.

Quinn has taken him up on that.

“I never look at it that I am going down to the old coach to see what he would do,’’ said Quinn. “I look at it that I’m going down to see a friend of mine and see what he would do. I’m very secure and comfortable seeing him every day. I’ve leaned on him for admissions advice, and for social advice when I’ve had to discipline kids. It’s been very helpful.’’

Parker, whose office is just down the hall from Quinn’s, said it was destined to be an uphill climb this season.

“No matter who the coach was going to be this year, it turned out to be a rebuilding season,’’ said Parker. “It shouldn’t have been but it turned out to be because we lost key guys. There should have been Charlie Coyle, Adam Clendening, Sahir Gill, and Matt Nieto in the senior class and that would’ve made night and day what type of team this would’ve been.’’

Coyle is playing center for the Minnesota Wild; Clendening, a Blackhawks draftee, is playing for the Rockford IceHogs of the AHL; and Gill is playing for the Wheeling Nailers of the ECHL.

“When you get those guys out, you bring in freshmen. When you lose Nieto who would’ve been a 21-year-old senior, you replace him with an 18-year-old instead of having him wait a year and come in as a 19-year-old freshman. Both Nieto and Gill were left-shot forwards who could’ve played left wing. That’s a position we’re really thin at and really young.’’

One of the players who made sacrifices was senior defenseman Garrett Noonan.

“I knew it was it was going to be a little bit of a transition year and a little bit of a rebuild,’’ said Noonan. “All programs have to do that at some point but I wanted to be part of the solution. We had our fair share of losses but I think the job Coach Quinn has done is amazing. He did a great job of knowing when to be hard on us and when to lay off. It’s obviously been a little bit of a tough year but we have some time here to figure this out if we can get a win here this weekend and try to salvage the season.’’

Despite the struggles, Quinn has all the confidence of the administration and, aside from a few impatient fans, all the friends of BU hockey.

“Those are big shoes to fill and David knew that coming in but I also think he’s more than ready to take that mantel on,’’ said athletic director Mike Lynch. “A lot of the things you’ve seen happen to our team happen to every team. Last weekend was a good indicator of how our guys have really bought into what David is trying to do and I certainly have a pretty good handle on where we’re going in the future in terms of the types of kids he’s been recruiting, so the future is bright but it is a transition period. This year is best defined in my mind as one step backward and two steps forward. Because of the transition, we’re getting a great amount of playing time from all of our young guys, our goalies have been fantastic. Looking forward, we know the class we hope to have here next year and putting those pieces together, we’re going to take those two steps forward next year and the year after. The future looks really bright.’’

The brimming optimism doesn’t mean there haven’t been some very trying moments.

“I’m very lucky because people are very realistic about where we’re at,’’ said Quinn. “But I’m still the head coach and we didn’t have the season we wanted to have so it doesn’t make me sleep any better. It’s been tough but we have shown remarkable optimism and resilience. For a team that has struggled like we have, there is great morale. It has been stressful but in my alone time every now and then I say, ‘I’m the head hockey coach at BU.’ It is a job a lot of people would die to have and I know how lucky I am. I never take it for granted.’’